A turntable has been used heretofore in order to rotate and drive a disk-like recording medium, for example, an optical disk, such as a compact disk (CD), or a Digital Versatile Disk (DVD).
As a turntable for mounting an optical disk thereon to rotate and drive it, the turntable constituted as shown in FIG. 1 is used. In the turntable 1000, an optical disk D is fitted in a centering portion 1002 formed with a centre hole 1001 in a centre portion of the turntable 1000, whereby the optical disk D is mounted on the turntable 1000. The centering portion 1002 is formed into a convergent trapezoid in the circumferential surface with an elastic displacing element 1004 elastically displaced in a diametrical direction and a fixed element 1003 alternately there around. The inner peripheral surface of the centre hole 1001 is pressed and supported by the elastic displacing element 1004 and placed in contact with the fixed element 1003 to coincide the rotational centre with a rotational centre CL of the turntable 1000, and the optical disk D is mounted on the turntable 1000.
A magnet 1005 is provided on the centering portion 1002 of the turntable 1000. The magnet 1005 magnetically attracts a chucking portion (not shown) to hold the optical disk D in cooperation with the turntable 1000. A yoke 1006 is provided on the lower side of the magnet 1005. The centering portion 1002 is secured to the turntable 1000 by pressing, and the turntable 1000 is mounted on a drive shaft 1008 of a spindle motor 1007 by pressing. The elastic displacing element 1004 for carrying out the centering operation of the optical disk D provided and mounted on the centering portion 1002 is formed of a creepless material, such as PEI (poly ether imido), which is hard to produce the creeping phenomenon in order to prevent the creeping phenomenon from occurring in the state that the optical disk D is mounted so as not to return to the original state.
The turntable 1000 heretofore used has the construction in which the centering portion 1002 is pressed into the centre portion and pressed into the drive shaft 1008 to mount it. That is, since the centering portion 1002 and the turntable 1000 are formed from a separate member, not only assembling is difficult, but also mounting aimed at centering for allowing the centre of the centering portion 1000 to coincide with the centre of the drive shaft 1008 is difficult.
There is a further problem that since a creepless material, such as PEI (poly ether imido), is high in molding temperature, injection molding of the centering portion 1002 cannot be carried out in the state that the magnet 1005 is put into a molding mold. When the magnet 1005 is exposed to a high temperature atmosphere, demagnetization occurs, and, therefore, the centering portion 1002 cannot be molded with the magnet 1005 inserted. Therefore, the magnet 1005 is fixed by adhesion after the centering portion 1002 has been molded. Since such a magnet 1005 is adhered, the assembling step of the centering portion 1002 becomes complex, leading to a higher cost, and, further, also posing a problem in reliability in terms of assembly.
Further, when the optical disk is mounted on the turntable and rotated continuously, it also is necessary to prevent the optical disk from slipping with respect to the turntable. That is, the optical disk needs to be rotated and driven integral with the turntable.